1. Field of the Invention
The present invention relates to a container stopper, and a manufacturing method therefor, in which a liquid-contact surface and an outer peripheral surface continuous with the liquid-contact surface of a core formed of an elastic material are coated with a synthetic resin skin.
2. Description of Related Art
As stoppers used for containers of whiskey and wine, for example, compressed cork stoppers, which are formed by blending an adhesive to cork grain made to an appropriate grain size, then heating and pressurizing it to form a compressed cork plate or compressed cork material, and punching or cutting it to a desired shape, and natural cork stoppers, are widely used conventionally.
However, with the conventional cork stoppers, although surface treatment is done with wax, silicone oil or the like, the cork is in a bare state. Therefore, when the cork is contaminated by mold smelling substances, typically trichloro-anisole (TCA), they could diffuse into the whiskey or wine in the containers to spoil the taste of the contents. In addition, cork dust could fall into the contents.
Furthermore, the contents could soak into the cells of the cork to discolor the outer surfaces of the cork stoppers. Where the contents contain alcohol, lignin and suberin which are components of the cork could diffuse to the alcohol, causing the cork stoppers to become “thin”, thereby lowering their physical strength and sealing effect.
Also, a container stopper has been proposed in which natural cork or compressed cork is used as the core of the stopper. The liquid-contact surface and the outer peripheral surface continuous with the liquid-contact surface of the cork core are coated with a polyethylene skin. Further, only the liquid-contact portion of the polyethylene skin is coated with a circular sheet made of polyethylene terephthalate (see U.S. Pat. No. 2,973,249, for example).
According to this conventional technique, the above-mentioned problem such as of trichloro-anisole contained in the cork diffusing into the contents is avoided. However, the flavor of the contents could be spoiled by various types of smells entering from outside the container or by absorption or adsorption of the flavor of the contents.
That is, although the liquid-contact surface of the core is coated with a sheet of polyethylene terephthalate, the outer peripheral surface, i.e. the portion that contacts the inner peripheral surface of the opening of the container, is coated with a skin of polyethylene. Since polyethylene is porous and has a property of absorbing and adsorbing smell, when stored in a warehouse, closet or the like, mold smelling substances, typically TCA, present in such an environment, and smell components such as naphthalene contained in an insecticide, could pass between the inner peripheral surface of the opening of the container and the stopper to be absorbed or adsorbed by the polyethylene to adversely affect the taste of the contents with the progress of time. Conversely, the flavor of the contents may be absorbed or adsorbed by the polyethylene, which would adversely affect the taste of the contents. There is room for improvement in this respect.
Naturally, a container stopper, when inserted into the opening of a container, is required to have a function for completely preventing leakage of the contents. However, where only the outer peripheral surface of the core is coated with a skin of polyethylene terephthalate to solve the above-noted problem, a reduction in diameter of the core inserted into the opening of the container results in “creases” being formed on the skin of polyethylene terephthalate covering the peripheries. The “creases” become a cause of leakage of the contents.
This invention has been made having regard to the disadvantages of the prior art noted above, and its object is to provide a container stopper, and a manufacturing method therefor, capable of reliably preventing adverse influences of various smells entering from outside the container and absorption and adsorption of the flavor of the content, as well as preventing adverse influences of a core such as cork.